The use of high oriented and low oriented fiber blends in the same fabric is known in the textile art. Low oriented fibers are more susceptible to the action of heat, solvents, reactants, dye stuffs, and adhesives, and in many instances can be employed to aid fusion bonding or otherwise modify fabric properties. In order to increase the tenacity of high polymer strands such as those produced by melt-spinning nylon, it has been the usual practice to draw them to textile filaments of high strength, under temperatures of 20.degree. to 300.degree. C. whereby the fiber molecules are oriented and the fibers made stronger, more durable, etc. The drawing extension used varies from slightly over 1 to 1 to 11 to 1 or more to suit the particular polymer structure, molecular weight, crystalline properties, etc. It was discovered early that to gain adequate and uniform strength for subsequent processes in every segment along the filament length, certain polymer types, such as the nylons, polyesters, polyolefins, etc., must be drawn to a certain minimum draw ratio. This minimum extension became known as "natural draw ratio" to the art. By "natural draw ratio" is meant that draw ratio which is reached just prior to a sharp increase in pulling force being required to further extend or stretch a filament. This property can be the conventional plotting of a stress-strain curve during drawing of an undrawn filament. Natural draw ratio is defined by Marshall and Thompson, J. Applied Chemistry 4, 145 (1954). The actual numerical value of "natural draw ratio" varies with polymer properties, extrusion conditions, and drawing conditions for any specific polymer type.
The instant invention violates several of the classic concepts of drawing to achieve a novel, useful product, i.e., by drawing at a temperature below accepted minimum temperatures, even those used for so-called "cold draw". The term "cold draw" as generally referred to in the art is inaccurately named since conversion of mechanical energy to thermal energy during drawing imparts heat to the filaments at the actual draw point. The novel product of this invention is produced by attenuation of the filaments below the natural draw ratio of the given filaments without imparting strand portions of variable diameter which are too weak for further processing by usual means. This quite unexpected result appears to be due to a fixation of the essentially unoriented thick section structure so it will not readily extend under stress as a normal unoriented structure is prone to do. The most significant, novel property of the fibers of this invention is that a random distribution of sections of unlike cross-sectional area produces certain desired properties without sacrificing other desirable properties. These unlike sections are comprised of oriented and unoriented molecules, respectively, whereby the fibers and fabric containing the same have drawn and undrawn yarn characteristics. Thus, besides the variation in cross-section size, the filaments of this invention show variations in dye receptivity, sheen, elasticity, and sticking temperature between small and large diameter segments.